Method for maximizing the value of carbonaceous material

ABSTRACT

A method for pyrolyzing coal to produce a raw hydrogen-rich gas and a hot char composed of carbon that is divided into two streams, one gasified to make a second gas and one reacted with steam to produce hot activated carbon that is divided into a first sub-stream and a second sub-stream. 
     The hydrogen rich gas, after cleanup, is converted to methanol which, in turn, is synthesized into gasoline or synthetic natural gas. The second gas, after clean-up, fuels a turbine to generate electricity while exhausting a flue gas (N 2 +CO 2 ) that is reacted with the first sub-stream of hot activated carbon and with hydrogen for synthesis into urea (CO(NH 2 ) 2 ). 
     The urea is mixed with the second sub-stream of activated carbon to produce a fertilizer which is introduced into soil to store plant nutrients. 
     This process produces fuel, electricity, and enhancement of plant growth.

BACKGROUND OF THE INVENTION

This invention relates to a clean and efficient poly-generation ofvarious valuable products from carbonaceous materials such as bituminouscoal, sub-bituminous coal, lignite, peat, coke, biomass, etc. Thisinvention which is a continuation-in-part of the Applicant's pendingpatent application bearing Ser. No. 11/506,939 filed on Aug. 21, 2006,relates to the co-production of enhanced fuels and efficient electricpower while mitigating the ill-effects caused to the environment byutilizing said carbonaceous materials as combustible fuels, particularlywith respect to emitting carbon dioxide (CO₂) into the atmosphere. CO₂is commonly referred to as a “greenhouse gas” and is suspected ofcontributing to global warming. Specifically, this invention is animprovement of the Applicant's issued patent bearing No. 6,911,058 B2issued on Jun. 28, 2005; this patent fails to address theever-increasing ill effects to the environment caused by the emission ofgreenhouse gases, in particular by carbon dioxide (CO₂).

Attempts are being made to capture CO₂ where it is generated and tosequester it by introducing it under pressure into such places as deepwells and underground reservoirs for permanent storage—a costly,inefficient and questionable solution, except in cases wherein it isinjected into oil or gas wells in order to recover residual oil or gasfrom such wells; however, the infrastructure related to the pipingnecessary to transport the CO₂ to such wells is a major disadvantage;there is no assurance that CO₂ will not leak out via fissures in suchwells.

The Applicant has discovered a method herein disclosed that reduces theformation of CO₂ by being efficient while still using said carbonaceousfuels, and especially coal, and at the same time converting CO₂ into auseful by-product such as urea, a valuable fertilizer that enhances thegrowth of biomass, a renewable energy resource in the agriculturesector.

Before listing the objectives of the instant invention and proceedingwith its description, coal will be used as the energy resource as anexample, since more than four billion tons of coal are combusted yearlyworldwide, but the instant invention is applicable to the use ofcarbonaceous materials in general.

OBJECTIVES OF THE INVENTION

The main object of the instant invention is to maximize the value ofsaid carbonaceous materials by making their efficient use possible andyet mitigating the ill-effects that they cause to the environment.

Another object of the instant invention is to extract from the coal viapyrolysis a raw hydrogen rich gas which, after cleanup, is used as aresource to make valuable and sorely needed products such as gasoline orsynthetic natural gas (SNG) while at the same time producing a hot char.

Still another object of the present invention is to gasify a firststream of the hot char with air preferably, to produce a raw lean gaswhich, after cleanup, becomes an excellent fuel for combustion turbineswhich, when configured in a combined cycle mode, generate electric powermost efficiently by virtue of mass and low NO_(X) formation whileemitting a flue gas composed mainly of nitrogen and carbon dioxide(N₂+CO₂).

Yet another object of the instant invention is to pass steam through asecond stream of said hot char in order to transform it to activatedcarbon.

Therefore another object of the instant invention is to divide saidactivated carbon into two sub-streams wherein a “first” sub-stream isset aside for export to the agriculture sector for introduction intosoils to stimulate more vigorous growth of crops by providing a cellularstructure to store plant nutrients while at the same time sequesteringcarbon in Mother Earth whence it originated.

Therefore another object of the instant invention is to elevate thetemperature of the “second” sub-stream of said activated carbon toenable it to react with nitrogen (N₂) to thus activate the N₂.

Further another object of the instant invention is to use off-peak powerto electrolyze water to co-produce hydrogen (H₂) and oxygen (O₂).

Further still another object of the instant invention is to react hotactivated carbon (C) with flue gas (N₂+CO₂) and with hydrogen (H₂) tomake urea (CO(NH₂)₂) while at the same time sequestering CO₂ via theformation of urea, such as CO₂ being produced in the generation ofelectric power.

Further yet another object of the instant invention is to mix activatedcarbon with urea to make a super-fertilizer.

Therefore yet another object of the instant invention is to utilize theO₂ derived from electrolysis to serve as the oxidant in the pyrolysis ofthe coal.

It is yet another object of the present invention to mix said hydrogenrich gas and said lean gas to create a fuel suitable to co-produceelectric power and urea while sequestering carbon in the soil.

It is still another object of the present invention to mix said hydrogenrich gas and said lean gas to create a fuel suitable to generateelectric power while activated carbon is sequestered in soil.

These and other objects of the present invention will become moreapparent to those skilled in the art to which this invention pertainsfrom the following description and appended claims. Reference is nowbeing made to the accompanying drawings forming a part of thisspecification. It is to be noted that the embodiments shown herein arefor the purpose of description and not limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process-flow diagram in block form of the invention with thecomponents and process streams being numerically identified.

FIG. 2 is a process-flow diagram in block form of the invention with thecomponents and process streams being identified with words.

Before proceeding with the detailed description of the invention bymaking use of the drawings, it is to be noted that for the sake ofclarity reference will be made to the numerals and to the words torepresent the various components and process streams.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, numeral 10 denotes a pyrolysis chamber and numeral11 a char gasifier; numeral 12 denotes a gas clean-up system for thehydrogen rich gas from pyrolysis, and numeral 18 denotes a gas clean-upsystem for lean gas made in gasifier 11; numeral 13 represents amethanol plant and numeral 14 represents a gasoline conversion plant;numerals 15, 16, and 17 represent a combined-cycle power generationassembly with numeral 15 denoting a gas turbine, numeral 16 denoting aheat-recovery steam generator and numeral 17 denoting a steam turbine;numeral 21 represents a rectifier to change the power from alternatingcurrent to direct current and numeral 19 represents an electrolysischamber to split water into H₂ and O₂. Numeral 20 denotes a urea plantfor synthesizing hot activated carbon, flue gas (N₂+CO₂) and hydrogeninto carbon monoxide and urea—namely CO+CO(NH₂)₂. Numeral 63 is a charactivator to make activated carbon and numeral 64 represents a reheaterto reheat the activated carbon.

Before describing the operation of the instant invention, it is to benoted that the various streams incorporated in the method would includepressure boosting and pressure let-down equipment, such as compressors,expanders, and miscellaneous valves as required, depending upon theprevailing conditions to enable the navigation of the flow of eachstream. Since the use of such equipment is common practice in the fieldof chemical engineering and is known in the art to which this inventionpertains, the Applicant has obviated the inclusion of such equipment inthe drawings, even though such equipment will be used in the applicationof the instant invention.

Operation

Assuming that the process is already at steady state and referring toboth FIGS. 1 and 2 in combination, coal denoted by stream 60 is fed intopyrolysis chamber 10 wherein O₂—stream 22 is injected into it to such anextent as to combust a small portion of the coal to generate the thermalenergy required to devolatilize the coal to yield a rich raw gas havinga high H₂ content—stream 23, which is directed to rich gas cleanupsystem 12. By controlling the O₂ input into chamber 10, the conditionswithin pyrolysis chamber 10 are maintained highly reducing whileconverting the coal into a hot char which is divided into two parts,stream 27 and stream 31. Stream 27 is fed into gasifier 11 where it isreacted preferably with air, stream 51 which is derived from thecompressor (not shown) of gas turbine 15, thus converting the carbon inthe hot char into a hot raw lean gas—stream 67 and slag—stream 26. Hotchar, being mostly carbon and highly reactive by virtue of its cellularand porous structure, is efficiently gasified with air.

Hot char stream 31, the second part of the char from stream 24, isdirected to the activator denoted by numeral 63 for converting the hotchar into activated carbon by means of steam-stream 33; stream 66denotes the off-gas from activator 63; stream 55 represents theactivated carbon discharged from activator 63. During the activation ofthe hot char with steam, it loses temperature by virtue of the water-gasreaction that takes place.

Activated carbon stream 55 is, in turn, further divided into sub-stream58 and sub-steam 61, with sub-stream 58 being fed into reheater 64 wherethe temperature of the activated carbon is raised by making use of theelevated temperature of the hot, raw lean gas-stream 67, by directlycontacting the activated carbon contained in reheater 64. The partiallycooled raw lean gas leaves reheater 64 as stream 25 and is directed tolean gas cleanup 18. In both cleanup systems 12 and cleanup 18, thesulfur in the gases is removed, and it leaves cleanup 12 via stream 28and cleanup 18 via stream 29; these two sulfur streams join to formstream 44.

The cleaned rich gas which essentially is CO+2H₂ leaves cleanup 12 viastream 46 and is directed to methanol plant 13 where the rich gas isconverted to methanol which, in turn, is directed as stream 47, togasoline plant 14 where the methanol is converted to gasoline via ExxonMobil's process known as “MTG” for short. The clean lean gas whichessentially is N₂+CO leaves cleanup 18 via stream 30 to which CO—stream48, is added to form stream 32 which fuels gas turbine 15; air tocombust stream 32 is furnished by stream 52 which is compressed prior toentering the combustion chamber (not shown) of gas turbine 15. The fluegas exhausting from the gas turbine is passed through heat recoverysteam generator 16 to raise steam which is directed to steam turbine 17via stream 50. Both gas turbine 15 and steam turbine 17 are eachfollowed by a generator (not shown) to generate electric power mostefficiently via the combined cycle mode which power leaves as streams 37and 38, respectively, to form stream 39. The flue gas leavingheat-recovery steam generator 16, which is made up of nitrogen andcarbon dioxide (N₂+CO₂) is denoted by stream 34. A portion of the steamgenerated in heat-recovery steam generator 16 is withdrawn as a sidestream which is denoted by numeral 36; this side stream of steamtogether with H₂ stream 49 form stream 53 which is directed tohigh-temperature electrolysis system 19 in order to increase theefficiency of H₂ generation. It is to be noted that side stream 36 mayalso be withdrawn from steam turbine 17.

An alternating electric current stream denoted by numeral 40 is directedto rectifier 21 where it is converted to direct electric current to formstreams 42 and 43 which are introduced into electrolysis system 19 inorder to electrolyze the steam contained in stream 53 to yield a largeroutput of H₂-stream 56 and also producing O₂ as stream 22; this largeroutput of H₂ is directed to synthesis system 20, while the O₂, afterbeing compressed (not shown), is directed to pyrolysis chamber 10 asstream 22.

Referring now to the flue gas, stream 34 (N₂+CO₂) is split to create ableed of flue gas to maintain system balance denoted by numeral 35, toresult in stream 57 which joins H₂ stream 45 (the net H₂ produced inelectrolysis system 19) to form stream 65. The activated carbon(C)—stream 68 and the flue gas (N₂+CO₂) together with the H₂—stream 65are respectively introduced into urea plant 20 to produce urea(CONH₂)₂)+CO as stream 69. The CO, as stream 48, is separated fromstream 69 to result in the formation of urea as stream 59 whence thisstream joins activated carbon sub-stream 61 to form a super-fertilizerfor export denoted by stream 62.

It is to be noted that the hot activated carbon may be reacted with theflue gas by itself in a reactor to form CO and cyanogen (C₂N₂), and theH₂ may then be added in a subsequent reaction to form the urea. Further,the formation of urea may also occur via the ammonia (NH₃) route byreacting N₂ with 3H₂ to make 2NH₃ and subsequently reacting the 2NH₃with CO₂ to form CO(NH₂)₂+H₂O, the conventional method of making urea.

The step of making urea may be obviated by making use of the method tomake activated carbon from a portion of the char, activating suchportion, and sequestering it in the soil to enhance it by introducingcellular structure to store plant nutrients and to provide time releaseof such nutrients to result in causing the vigorous growth of plantlife.

In summation, it is submitted that the method described herein formaximizing the benefits derived from a carbonaceous material such ascoal which contains sulfur in an environmentally acceptable manner whileco-producing liquid fuel, electric power and urea is comprised ofpyrolyzing the coal with oxygen to produce a raw hydrogen (H₂) rich gasand a hot char which is cellular in structure and substantially composedof carbon (C). The hot char so produced is divided into two streams,with the first stream being directed to a gasifier that is air blown tomake a raw lean gas which is made up of nitrogen and carbon monoxide(N₂+CO) and a second stream being activated with steam to produceactivated carbon that is further divided into a “first” sub-stream ofactivated carbon and a “second” sub-stream of activated carbon whose usewill be described hereinafter.

Subsequent to the cleaning of the H₂ rich gas and the lean gas,including the removal of mercury from these gases, the cleaned H₂ richgas (syngas) may be converted to one or more chemicals, but preferablyto methanol which, in turn, is converted to a transportation fuel suchas gasoline, a most valuable liquid fuel. The cleaned lean gas fuels agas turbine that is part of a combined-cycle system to generate electricpower most efficiently by virtue of its large N₂ content whichcontributes a large mass flow of gases through the gas turbine whileexhausting an off-gas (flue gas) made up of N₂+CO₂. This flue gas whichis reacted with activated carbon and H₂, is synthesized with 2H₂ toproduce urea which is characterized chemically as NH₂.NH₂.CO or CO(NH₂)₂plus CO. Alternatively, the formation of the urea may be theconventional route of making urea by first forming ammonia (NH₃) and, inturn, reacting two molecules of NH₃ with CO₂ to form CO(NH₂)₂, and H₂Oas by-product; in this case, the N₂ in the flue gas is separated fromthe CO₂ prior to reacting with the NH₃.

Preferably during off-peak periods, the excess of the electric powerthat can be generated for which there is no demand, such power isutilized to electrolyze steam in a high-temperature electrolysis systemto generate H₂ and O₂, with the H₂ produced being the source for the H₂needed in synthesizing the N₂+CO₂ (with the aid of hot activated carbon)into urea. Preferably, some of the H₂ produced via electrolysis isrecycled with the steam fed to the electrolysis system to enhance theproduction of H₂. The O₂ which is co-produced via electrolysis is usedin the pyrolysis of the coal mentioned above.

The “first” sub-stream of activated carbon serves to activate N₂ in theflue gas (N₂+CO₂) to make possible the formation of urea according tothe following chemical reaction: (N₂+CO₂)+C+2H₂→CO+CO(NH₂)₂, wherein theCO is separated from the urea and is added to the lean gas to becomepart of the fuel for the gas turbine mentioned above.

The urea so formed is mixed with the “second” sub-stream of activatedcarbon, mentioned above, to produce a super-fertilizer which is put intothe soil, not only for the sequestration of carbon (C) directly andcarbon dioxide (CO₂) indirectly via the urea, but also to providestorage for plant nutrients in the abundant cellular structure of theactivated carbon, thus:

-   -   Contributing to the efficient use of plant nutrients via their        storage in the cells of activated carbon:    -   Increasing plant yield via the conservation of the nutrients;        and,    -   Reducing CO₂ emissions by converting the CO₂ in the flue gas        into a component of the super-fertilizer while at the same time        sequestering a portion of the carbon from the coal back into the        soil.        From an economic standpoint, the formation of a super-fertilizer        made from low-cost carbon (char from coal pyrolysis), low-cost        hydrogen (electrolyzing steam with off-peak power), and flue gas        (a waste off-gas) can be sold to the farming community at a very        attractive price when compared to urea made from natural gas,        thus helping produce abundant plant life to retain water in the        soil that will increase forest land and abundant food for        mankind.

1. A method for maximizing the value of carbonaceous material in anenvironmentally acceptable manner comprising the following steps:pyrolyzing the carbonaceous material in an atmosphere which is deficientof oxygen to produce a first gas and a hot char which possesses acellular structure that is essentially made up of carbon; dividing saidchar into two streams comprising a first stream of char and a secondstream of char; gasifying said first stream of char to produce a secondgas; utilizing said first stream of gas and said second stream of gas asfuels for the formation of one or more than one subsequent form ofenergy while emitting a flue gas containing carbon dioxide (CO₂) intothe atmosphere, said CO₂ being a greenhouse gas and being suspected ofcausing global warming; and sequestering said second stream of char insoil in order to compensate for at least a portion of the CO₂ emittedinto the atmosphere while increasing the capability of the soil toretain nutrients in the cellular structure of the sequestered char toresult in an increase in the yield of plant growth from said soil, saidincrease of plant growth being a greater consumer of CO₂ than if saidsecond stream of char were not sequestered in the soil.
 2. The method asset forth in claim 1 wherein said first gas and said second gas arecleaned prior to the step of utilizing said gases as fuels for theformation of one or more subsequent form of energy.
 3. The method as setforth in claim 1 wherein said second stream of char is activated toconvert it to activated carbon by enhancing the capability of itscellular structure to absorb nutrients.
 4. The method as set forth inclaim 1 wherein said first gas is a hydrogen (H₂) rich gas which issuitable for making an upgraded chemical.
 5. The method as set forth inclaim 1 wherein the step of utilizing said first gas and second gas asfuels for the formation of one or more than one subsequent form ofenergy is further characterized by the step of utilizing both gases asfuels for electric power generation.
 6. The method as set forth in claim4 wherein said upgraded chemical takes the form of methanol.
 7. Themethod as set forth in claim 4 wherein said upgraded chemical takes theform of synthetic natural gas.
 8. The method as set forth in claim 6wherein said methanol is converted into a transport fuel.
 9. The methodas set forth in claim 8 wherein said transport fuel comprises gasoline.10. The method as set forth in claim 1 wherein the step of gasifyingsaid first stream of char to produce a second gas is furthercharacterized by the step of injecting an oxidant to implement the stepof gasifying said char to produce a hot second gas at an elevatedtemperature.
 11. The method as set forth in claim 10 wherein steam isinjected in addition to said oxidant.
 12. The method as set forth inclaim 10 wherein said step of injecting an oxidant comprises theinjecting of air to give said second gas additional mass and low NO_(X)formation properties when it is combusted.
 13. The method as set forthin claim 12 further comprising the use of said second gas with itsadditional mass to fuel a combustion turbine to efficiently generateelectric power.
 14. The method as set forth in claim 13 being furthercharacterized by said combustion turbine being part of a combined cycleconfiguration for the generation of electric power while emitting anoff-gas as a waste flue gas consisting mainly of N₂+CO₂.
 15. The methodas set forth in claim 14 wherein said combined cycle configuration isoperated at a full load continuously to generate the maximum amount ofelectric power despite off-peak period.
 16. The method as set forth inclaim 15 wherein the excess electric power generated during off-peakperiod is used to electrolyze water to produce economical H₂ and O₂. 17.The method as set forth in claim 16 wherein said water takes the form ofsteam that is electrolyzed in a high-temperature electrolysis system.18. The method as set forth in claim 17 wherein said high-temperatureelectrolysis comprises the recycling of H₂ with said steam to provide amore efficient electrolysis system in the production of H₂.
 19. Themethod as set forth in claim 14 wherein said flue gas consisting ofN₂+CO₂ is combined with H₂ generated via electrolysis to form a mixtureof flue gas (N₂+CO₂) plus hydrogen (H₂).
 20. The method as set forth inclaim 3 wherein the step of activating said second stream of char toconvert it to activated carbon is further characterized by the step ofsub-dividing said second stream of char into a “first” sub-stream and a“second” sub-stream.
 21. The method as set forth in claim 20 whereinsaid “first” sub-stream is heated in order to create a hot “first”sub-stream of hot activated carbon (C).
 22. The method as set forth inclaim 10 wherein said step of injecting an oxidant to implement the stepof gasifying said char to produce a hot second gas at an elevatedtemperature is further characterized by the step of directing said hotsecond gas to heat said “first” sub-stream of activated carbon referredto in claim 21 to increase its reactivity.
 23. The method as set forthon claim 19 wherein said mixture of flue gas (N₂+CO₂) plus hydrogen (H₂)is further combined with said “first” sub-stream of hot activated carbon(C) referred to in claim 21 to form urea.
 24. The method as set forth inclaim 23 wherein said urea is further mixed with said “second”sub-stream of activated carbon (C) referred to in claim 20 to form anenhanced urea for the vigorous growth of plant life.
 25. The method asset forth in claim 1 wherein said carbonaceous material is coal.
 26. Themethod as set forth in claim 14 wherein the step of emitting an off-gasas a waste flue gas consisting mainly of N₂+CO₂ is further characterizedby the step of separating the N₂ from the CO₂.
 27. The method as setforth in claim 26 comprises the reacting of the CO₂ with ammonia 2(NH₃)to form urea (NH₂.NH₂.CO) plus water (H₂O).
 28. The method as set forthin claim 1 wherein said carbonaceous material contains sulfur.
 29. Themethod as set forth in claim 1 wherein said first gas and said secondgas are combined, cleaned and utilized to generate electric power whileemitting a flue gas which is suspected to create a harmful effect to theenvironment.
 30. The method as set forth in claim 2 wherein said firstgas and said second gas are cleaned comprises the removal of mercuryfrom both gases.
 31. The method as set forth in claim 1 wherein saidfirst gas and said second gas are utilized for the poly-generation ofvarious products.